Posted on 01/24/2022 11:05:12 AM PST by zeestephen
L2 Final Insertion Burn will start at 2:00 PM ET - No live coverage I can find - Also - Scientists and engineers operating NASA's James Webb Space Telescope will answer questions about the mission's latest milestones in a NASA Science Live broadcast at 3 p.m. EST Monday, January 24, followed by a media teleconference at 4 p.m.
(Excerpt) Read more at nasa.gov ...
L2 is the invisible point in space where the gravitational pull from the Earth, Moon, and Sun all balance out.
I guess they don’t allow men to work on the JWST - 100% female ....
It has to station-keep to keep from flying off, L2 is only relatively-stable. However, it’s close enough to stable that it can station-keep with very little fuel. Moving in an orbit around the L2 point apparently makes it even easier to station-keep.
Apparently, it made it to where it was supposed to be, and everything is working. I gave it maybe a 50% chance that it wouldn’t or something of the hundreds of things it needed to happen wouldn’t work.
I’ll take my crow deep fried, thank you very much.
If space is a vacuum and there is no atmosphere, what does a rocket engine “push” against to propel the vehicle? It's always been a head scratcher for me.
I can’t believe it’s been 30 days since the launch.
Yes, I’ve read similar descriptions about ‘station keeping’. Something about this gravitational well or neutral point is significant in making orbital characteristics favorable but I don’t get the intuitive mechanics.
They are obviously not going to have a continuous fuel vector. Or maybe they will.. and only need a very tiny bit. But 10 years of doing that?
Basically, it’s a “saddle-point” (flat spot) in the gravitational potential field for orbiting objects. At the L2 distance, the spacecraft “sees” the gravity of earth and sun added together, so it can orbit a million miles further from the sun than earth, but still take the same 365+ days to orbit the sun that the earth does. It’s a “cheap” (in terms of fuel) spot to hang out and still maintain (about) the same distance from earth at all times.
It's not pushing against anything. It's expelling mass (rocket exhaust) in one direction and Newton's third law (conservation of linear momentum) says that the rocket has to move in the opposite direction. Exactly the same thing is responsible for the "recoil" or "kick" when you fire a rifle. It's not because the bullet is "pushing" on anything, it's because the bullet left the rifle barrel at high speed and the rifle moves in the opposite direction with the same momentum as the bullet (which, because the rifle is much heavier than the bullet, is a lot slower in velocity terms).
Maybe they put Webb Hubbell on board to add some extra weight.
;-)
Prepare to be assimilated.
I am not an engineer, but my take is that orbiting something that is in constant and slightly unpredictable motion requires less energy than trying to maintain an exact fixed distance from that same object.
There are also practical advantages for a telescope.
Relative to Earth, Webb is in a polar orbit around L2. The length of its orbit - north and south - is slightly larger than the orbit of the Moon - east and west - around Earth.
This solves two problems. First, Webb will never pass within the shadow of the Earth or Moon. A shadow would mean fluctuating electrical power, plus, temperature sensitive equipment would be constantly heating and cooling.
Second, Webb will have its insulated back side permanently facing the sun as it orbits, which means it can work 24-7 with an unobstructed view of the universe (every 12 months) except for the tiny piece of real estate between Earth and the Sun.
I’m just surprised no one has suggested the first images will be of Chelsea Clinton
Oh, that’s a good explanation. So the sun is always on the opposite side of earth from L2 so both of their gravities combine to curve space enough for Web to hangout with minimal effort. Web’s orbiting mechanics I have yet to fully get. TY
The executive summary is something like: there are various reasons why it's better to be close to L2 rather than to sit still at L2 all of the time. More sunlight (not in earth's shadow), better communications coverage, easier station-keeping, etc.
Once you offset from L2, earth's gravity "pulls" at an angle. That pull can be viewed as the vector sum of a component toward the sun and a component perpendicular to it.
The perpendicular component is the "pull" that keeps Webb in an orbit, just as though there were a real object at L2 to orbit around. (The toward-the-Sun component, of course, keeps Webb in an orbit around the Sun.)
Webb's orbit around L2 is very large; bigger than the moon's orbit around earth. It takes about 6 months to make the full trip around.
You’re half right. Newton’s third law applies to the entire system.
However, from the reference frame of a rocket, the expelled mass exerts a force on the rocket engine that must be reacted through the engine to the engine mounts, and up through the primary structure.
👍good stuff.. And thank you for the link.
Great link!
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